Monday morning, just blocks from the U.S. Capitol, a lone gunman opened fire at a naval office building, killing 12 people before he was fatally shot in a gun battle with police.

It was the latest in a growing number of massacres committed on unsuspecting Americans by people with easy access to firearms. The killer in this case was Aaron Alexis, a veteran of the Navy reserve who had worked on the Marine Corps and Navy intranet as an information technology contractor.

The 34-year-old Texan entered the Navy Sea Systems Command building at the Washington Navy Yard and, at about 8:20 a.m Monday, fired from a balcony onto office workers in the cafeteria below.

Alexis had a history of arrests for disorderly conduct and gun-related incidents, but managed to escape charges that could have possibly appeared in background checks. While a background check in Virginia prevented him last Saturday from purchasing an AR-15 assault rifle because he was an out-of-state buyer, it did not prevent him from purchasing an 870 Remington pump-action shotgun. He reportedly loaded the short-barreled “riot gun” with about a dozen large ball-bearing shots that splattered lead far and wide.

Alexis was arrested in Seattle in 2004 after he fired three shots from a Glock pistol into the tires of a car parked by construction workers near his driveway, and again in Fort Worth, Texas, in 2010 for firing a gun into the floor of his apartment after he reportedly complained to the resident below that she was too noisy. Alexis was not charged in either incident. He had also been arrested in 2008 in DeKalb County, Ga., for disorderly conduct. Alexis told Fort Worth police that he was cleaning his gun when it accidentally discharged. He told Seattle police that the construction workers had “disrespected” him when he shot out their car’s tires.

Alexis’ father told Seattle detectives that his son had anger management problems, possibly associated with post-traumatic stress disorder, because he “was an active participant in rescue attempts of Sept. 11, 2001.”

A Brooklyn, N.Y., native, Alexis was a full-time Navy reservist from May 2007 until January 2011 when he was honorably discharged after Navy officials had been pursuing a general discharge against him on a series of eight to 10 misconduct charges ranging from traffic offenses to disorderly conduct.

At one point Alexis “went to the VA to talk to them about mental-health issues. He was trying to get help, we think,” said a federal official. In August Alexis reportedly complained to police in Rhode Island that people were talking to him through the walls and ceiling and sending microwave vibrations preventing him from sleeping at the hotel where he was staying while doing military contract work. Police alerted officials at the naval station about Alexis’ behavior, but reportedly heard nothing from them.

Consequently, Alexis was able to purchase the Remington shotgun because there was no record of hospital admissions for mental illness.

He was also able to enter the Navy Yard with valid credentials because he had passed his employer’s background check.

Nine months ago, 20 children and six adults were gunned down by 20-year-old Adam Lanza with more than 150 rounds from an AR-15 style Bushmaster semi-automatic rifle at Sandy Hook Elementary School in Newtown, Conn.

The horrific massacre inspired U.S. Sen. Joe Manchin, D-W. Va., and Sen. Pat Toomey, R-Pa., to propose a bill requiring universal background checks for gun purchases. While their bill achieved a majority in the U.S. Senate, it did not achieve the super-majority self-imposed by the Senate to become law.

The need for more comprehensive gun control measures is clear considering how easily Alexis slipped through the cracks even with a background check. But since the failure of the Manchin-Toomey Senate bill, little has been heard on Capitol Hill about gun control reform.

If the recent massacres in Arizona, Connecticut, Colorado, Wisconsin, Florida and here in Pennsylvania don’t make the case for tighter gun control measures on Capitol Hill, then hopefully this latest tragedy at the Washington Navy Yard will resonate with legislators. How much closer to home does the carnage have to be to make them understand the need for common-sense gun control?